Call Us Today! 208-734-7426
2390 Rostron Circle | Twin Falls, ID 83301

Northwest Foam Products, Inc. EPS Specs

Physical Properties of Expanded Polystyrene (EPS)

Federal Specifications: ASTM C 578-92

Minimum and maximum allowable values.

 PropertyUnitsASTM TestType IType VIIIType IIType IX
Density, Nominal pcfC303 or D16221.00#1.25#1.50#2.00#
Density, Minimum pcfC303 or D16220.901.151.351.80
Density, Range pcfC303 or D16220.90-1.141.15-1.341.35-1.791.80-2.20
Thermal Conductivity K Factor@ 25° FBTU/(hr) (sq.ft.)(F/in)C177 or C5180.
Thermal Conductivity K Factor@ 40° FBTU/(hr) (sq.ft.)(F/in)C177 or C5180.240.2350.220.21
Thermal Conductivity K Factor@ 75° FBTU/(hr) (sq.ft.)(F/in)C177 or C5180.260.2550.240.23
Thermal Resistance R-value*@ 25° Fat 1 inch thickness4.354.544.765.00
Thermal Resistance R-value*@ 40° Fat 1 inch thickness4.174.254.554.76
Thermal Resistance R-value*@ 75° Fat 1 inch thickness3.853.924.174.35
Compressive 10% Deformation psiD162110-1413-1815-2125-33
Flexural Strength psiC20325-3030-3840-5050-75
Tensile Strength psiD162316-2017-2118-2223-27
Shear Strength psi18-2223-2526-3233-37
Shear Modulus psi280-320370-410460-500600-640
Modulus of Elasticity psi180-220250-310320-360460-500
Water Absorption %C272< 4.0%< 3.0%< 3.0%< 2.0%
Water Vapor Transmission Perm. InE962.0-5.01.5-3.51.0-3.50.6-2.0

*R-value means the resistance to heat flow. The higher the R-value, the greater the resistance to heat flow. Typical tested R-values are based on the data provided by Nova Chemical Co., BASF Corp., and Huntsman Chemical Company.

Additional Information on All Types
  • Maximum Service Temperature: Long Term Exposure 167 degrees Fahrenheit, Intermittent Exposure 180 degrees Fahrenheit
  • Oxygen Index: ASTM test D2863 = 24.0%
  • Coefficient of Thermal Expansion: ASTM Test D 696 = 0.000035in./(in.)(F)
  • Buoyancy-Flotation: Minimum 50lbs / Cubic Foot
  • Capillarity – None
  • Long Term Exposure 167° F, Intermittent Exposure 180° F
  • ASTM Test D 2863 = 24.0%
  • ASTM Test D 696 = 0.000035in./(in.)(F)
  • Minimum 50lbs / Cubic Foot
Building Code Classification

ICC ESR-1349
U.L. File #R12290 Control #85TO Classification BRYX

Flammability Warning

Expanded Polystyrene (EPS) materials sold for construction use have a fire retardant modifier, but are considered combustible, as are all organic materials. They must not be stored or installed near open flame or any other source of ignition. In addition, when EPS insulation board is installed in the interior of a structure, it must be protected by a proper thermal barrier, and the installer must review applicable local, state, and federal building codes to determine the correct thermal barrier for the particular application.

Adjoining Materials Warning

Expanded Polystyrene (EPS) is subject to attack by liquid solvent or some solvent base adhesives and other liquid products such as gas, diesel, etc. Care should also be taken to separate any coal tar pitch products or coal tar pitch vapors from any direct contact with EPS foam.